Product and process for sterilizing paper and pulp products



United States Patent PRODUCT AND PROCESS FOR STERILIZING PAPER AND PULP PRODUCTS No Drawing. Application November 20, 1951, Serial No. 257,429

Claims. (Cl. 92-3) by mesne assign- New York, N. Y.,

This invention relates to improved manufacture of pulp and paper products and particularly to the sterilization of pulp and paper products. More specifically, it provides novel compositions comprising phenylmercuric derivatives of carboxy methyl cellulose products which are substantive with and capable of imparting sterilizing properties to pulp and paper products as well as improved pulp and paper products produced by incorporation of the phenylmercuric derivatives of carboxy-methyl celluloses.

The present invention affords a simple and inexpensive means for rendering pulp, paper and similar materials sterile, that is, resistant to micro-organisms and capable of destroying on contact any micro-organism, pathogenic or not, which might come in contact with these materials. The pulp and paper materials treated may be in the form of newsprint, wrapping paper, paper plates and dishes, articles of personal hygiene made of paper or paper pulp, diapers, sanitary napkins, articles of apparel, and similar objects and materials. The articles thus treated will not irritate the human skin and will not cause toxic manifestations if accidentally ingested.

To better understand the basis of the present inven tion it is desirable to indicate the structure of the cellulose molecule.

(3112011 .5 at on. -0 n 3/! |\H on n (lJ o 1: l ji on; (|J O H\ l l /H 1h ()H DHIOH n H in; The monomeric unit of the cellulose molecule (hereinafter referred to as the anhydro-glucose unit) is that portion enclosed within the parenthesis of the above structural formula. The size of this cellulose molecule may vary considerably, but is usually of the order of about 200 to 600 anhydro-glucose units, i. e., n equals 200 to 600.

When reacted with chloroacetic acid or sodium chloroacetate in alkaline solution, cellulose gives the water soluble gum known variously as cellulose glycollic acid, carboxymethylcellulose, CMC, by way of examples. This product has been described and subsequently improved upon by various workers and has become a major article of commerce, being manufactured throughout the world to the extent of many millions of pounds annually.

H OH CHzOH The more common grades of carboxymethylcellulose being manufactured have a degree of substitution varying between about 0.45 and 0.75 of a CH COOM group per anhydro-glucose unit introduced at intervals along the cellulosic chain. Thus the more common molecules of carboxymethylcellulose may be visualized as consisting of about 200 to 600 of anhydro-glucose units, with an average of from 0.45 to 0.75 hydroxyl group per anhydro-glucose unit etherified with a -CH COOM group. However, less common molecules of carboxymethylcellulose may be used since the length of the cellulosic chain and its degree of substitution may be widely varied without departing from the spirit of my invention. The M in the substituted anhydro-glucose units is an alkali metal cation and is more commonly sodium, but sodium may be replaced by potassium or other alkali metals. For simplification, however, I have referred to M as sodium. According to the present invention, new phenylmercuric derivatives of carboxymethylcellulose are obtained by partial or complete 'substitution of the sodium cation in a sodium carboxymethylcellulose with a phenylmercuric cation; e. g. by reaction in aqueous phase with a water soluble salt of phenylmercuric hydroxide, e. g. phenylmercuric acetate. I have found that phenylmercuric carboxymethylcellulose is particularly active as a sterilization means but excellent agents for sterilizing pulp, paper and similar products are advantageously obtained by the substitution of the sodium cation in a sodium carboxymethylcellulose by the phenylmercuric cation to the extent of from about 5 to per cent of the total cation present.

The organic mercury compounds of the present invention are substantive to pulp and paper and will not leach out of such materials even on prolonged immersion or washing with water and render such paper permanently bactericidal and fungicidal. Because of the complexity of the new carboxymethylcellulose molecules it has been found desirable to refer to the percentages of the phenylmercuric cation organically bound in the form of the alkali metal-phenylmercuric carboxy-methylcelluloses. Preferably the new phenylmercuric compositions are incorporated into pulp and paper products to the extent of from about 0.0001 per cent to 0.1 per cent of the organically bound phenylmercuric cation on the basis of the dry weight of the paper. In such concentrations the compositions will not injure or adversely affect the human skin or cause undesirable irritation or allergic manifestations. For special purposes, however, much larger concentrations may be employed, but in any event the concentration of the phenylmercuric cation based on the total weight of the pulp or dry paper will be small and the proportion of the carboxymethylcellulose derivative will represent a minor proportion of the total weight.

The new phenylmercuric compositions may be prepared by reacting an aqueous solution (actually a colloidal gel) of sodium carboxymethylcellulose containing about 1 gram-equivalent of sodium cation with from about 0.05 to 1.00 gram-mole of a water-soluble salt of phenylmercuric hydroxide such as phenylmercuric acetate, phenylmercuric nitrate and the like. The products are obtained inthe form of a precipitate of phenylmercuric carboxymethylcellulose or a complex sodio-phenylmercuric carboxymethylcellulose. The new compositions are white amorphous solids which are insoluble in water and organic solvents. In strong mineral acids, the new compositions decompose with the liberation of free carboxymethylcellulose and the corresponding mineral acid salt strong of phenylmercuric hydroxide. When combined with strong caustic soda, they decompose with liberation of water-soluble sodiophenylmercuric hydroxide and the original sodium carboxymethylcellulose.

When the usual commercially available grades of carboxymethylcelluloses are used as starting materials, the new phenylmercuric carboxymethylcelluloses may be considered as cellulose molecules containing from about 200 to about 600 anhydro-glucose units, with an average ofabout 0.45 to 0.75 hydroxyl per anhydro-glucose unit etherified with a CH2COOM group and with the M cation varying from about 5 per cent phenylmercuric cation plus 95 per cent alkali metal cation in the molecule to per cent phenylmercuric cation in the molecule,

that is where the phenylmercuric cation is present to the extent of at least about 5 per cent of the total of carboxy-linked cations.

The new phenylmercuric carboxymethylcellulose compositions may be incorporated in thepulp to produce improved pulp and paper products by adding the agent in the desired amount to the pulp in the conventional beater box in the mill. The application may be made at or near room temperature 'or hot if desired. The method of incorporation may be widely varied however since the agents may be also incorporated at any convenient prior or subsequent stage in the paper making process, for instance, by spraying on the sheets of finished paper, by incorporation with the paper size or by other appropriate means of application or incorporation with the paper or pulp.

The following examples are given to illustrate the present invention, but not to limit it to the particular reagents, proportions or conditions described.

Example I 18.5 grams of phenylmercuric acetate is stirred, in small portions, with vigorous agitation into one liter of a hot 8% solution of low-viscosity sodium carboxymethylcellulose. After three hours of stirring, a uniform gel of phenylmercuric sodio-carboxymethylcellulose is obtained, in which about 40% of the sodium has been substituted by the phenylmercuric cation and 60% remains as the sodium cation. One part of this gel is incorporated into the beater per 150 parts of pulp (dry weight) and thereafter becomes an integral part of the paper article produced from the pulp. The paper product contains the equivalent of 0.01% of organically bound phenylmercuric ion.

Example 11 is incorporated into the beater per 750 parts of pulp (dry weight) and thereafter becomes an integral part of the paper article produced from the pulp. The paper product contains the equivalent of 0.001% of organically bound phenylmercuric ion.

Example III 45.0 grams of phenylmercuric acetate is stirred, in small portions, with vigorous agitation into two liters of a hot 4% solution of high-viscosity sodium carboxyme'thylcellulose. After three hours of stirring, a uniform gel of phenylmercuric carboxymethylcellulose is obtained. One part of this gel is incorporated in the beater per 170 parts of pulp (dry weight) and thereafter becomes an integral part of the paper article produced from thepulp. The paper product contains the equivalent of 0.01% of organically bound phenylmercuric ion. In this product, about 95% to 100% of the sodium has been substituted by the phenylmercuric cation.

In order to test the germicidal or fungicidal properties of the products prepared by the use of the new compounds of the present invention, sheets of paper containing 0.0001 percent, 0.001 per cent, 0.01 per cent and 0.1 percent of phenylmercuric cation organically bound as phenylmercuric sodio-carboxymethylcellulose were dried at charomyces cerevisiae (American Type Culture Collection #4110), After five minutes, scrapings of each inoculated area were transplanted on nutrient agar plates. In no case was it possible to obtain a viable transplant, thus indicating the complete destruction of the micro-organisms in each case.

In order to test the substantivity and leaching resistance of the above treated paper samples, each sample was leached in running water for one week, then carefully dried and the above tests repeated. The results were the same, i. e., in no casewasit possible to'obtain a viable transparent of the inoculated micro-organisms.

I claim:

1. Phenylmercuric carboxymethylcellulose.

2. A phenylmercuric alkali metal-carboxymethylcellulose in which the phenylmercuric cation is present to the extent of at least about 5% of the total of carboxy linked cation.

3. A phenylmercuric sodio-carboxymethylcellulose in which the phenylmercuric cation is present to the extent of at least about 5% of the total of carboxy linked cation.

4; A phenylmercuric carboxymethylcellulose in which about 0.45 to 0.75 hydroxyl per anhydro-glucose unit of the-cellulose molecule is substituted with a -CH2COOM group and in which the cation M contains from about 5% of a phenylmercuric ion and about of an alkali metal to about of the phenylmercuric ion.

'5. The composition of claim 4 wherein the alkali metal is sodium.

6. Sterile paper pulp in which has been incorporated in minor-amount as an essential component a phenylmercuric alkali metal-carboxymethylcellulose in which the .phenylmercuric cation is present to the extent of at least about 5 of the total of carboxy linked cation.

7. Sterile paper pulp in which has been incorporated in minor amount as an essential component a phenylmercuric carboxymethylcellulose in which about 0.45 to 0.75

hydroxyl per anhydro-glucose unit or the cellulose.

molecule is substituted with a CH2COOM group and in which the cation M contains from about 5% of a phenylmercuric ion and about 95 of an alkali metal to about 100% of the phenylmercuric ion. v

8. Sterile paper in which has been incorporated in minor amount as an essential component a 'phenyl mercuric alkali metal-carboxymethylcellulose in which the phenylmercuric cation is present to the extent of at least about 5% of the t'otalof carboxy linked cation.

9. Sterile paper in which has been incorporated in minor amount as an essential component a phenylmercuric carboxymethylcellulose in which about 0.45 to 0.75 hydroxyl per anhydro-glucose unit of the cellulose mo'lecule'is substituted with a -CH2COOM group and in which the cation M contains from about 5% of a phenylmercuric ion and about 95% of an alkali metal to about 100 of the phenylrnercuric ion.

10. Sterile paper in which has been'incoi'poratedas an essential component a phenylniercuric alkali metal-can" 'boxymethylcellulose in'whic'h'the phenylniercuric cation is room temperature for a week. Each sheet was then inoculated with several drops of' viable cultures of Escherichia coli (American Type Culture Collection present to the extent of at least about 5% of the'tot'alof carboxy linked cation in an amount'providing from about 0.0001%" to about 0.1% organically bound phenylme'rcuric on the dr'y'weight of the paper.

Referen'ces'Cited in the file of this patent U'NiTED STATES PATENTS 2,249,754" Ellsworth et a1. July 22,1941 2,349,797" Bock E May 30, 1944 2,400,544 Kline May 21,1946 2,416,447 Laughlin et a1 Feb. 25, 1947 Gillaspie Aug. 14, -1 

1. PHENYLMERCURIC CARBOXYMETHYLCELLULOSE.
 8. STERILE PAPER IN WHICH HAS BEEN INCORPORATED IN MINOR AMOUNT AS AN ESSENTIAL COMPONENT A PHENYLMERCURIC ALKALI METAL-CARBOXYMETHYLCELLULOSE IN WHICH THE PHENYLMERCURIC CATION IS PRESENT TO THE EXTENT OF AT LEAST ABOUT 5% OF THE TOTAL OF CARBOXY LINKED CATION. 